The radio frame in a Long Term Evolution (LTE) system includes Frequency Division Duplex (FDD) mode and Division Duplex (TDD) mode. As shown in FIG. 1, in the frame structure in the FDD mode, one radio frame of 10 ms is composed of 20 time slots, wherein the length of each time slot is 0.5 ms and the 20 time slots are numbered from 0 to 19; the time slots 2i and 2i+1 compose a subframe i, the length of which is 1 ms. As shown in FIG. 2, in the frame structure in the TDD mode, one radio frame of 10 ms is composed of two half frames, wherein the length of each half frame is 5 ms; one half frame includes 5 subframes, wherein the length of each subframe is 1 ms; the subframe i is defined as two time slots 2i and 2i+1, wherein the length of each time slot is 0.5 ms. In the above-mentioned two frame structures, for a Normal Cyclic Prefix (Normal CP), one time slot includes 7 symbols, wherein the length of each symbol is 66.7 us, and a CP length of the first symbol is 5.21 us, and lengths of the rest 6 symbols are 4.69 us; for an Extended Cyclic Prefix (Extended CP), one time slot includes 6 symbols, wherein the CP lengths of all the symbols are 16.67 us.
The release number of the LTE corresponds to R8 (Release 8), the release number corresponding to the addition release thereof is R9 (Release 9), as regards a latter LTE-Advance, its release number is R10 (Release 10). Three types of downlink physical control channels are defined in the LTE as follows: a Physical Control Format Indicator Channel (PCFICH), a Physical Hybrid Automatic Retransmission Request Indicator Channel (PHICH), and a Physical Downlink Control Channel (PDCCH).
The information carried by the PCFICH is used for indicating the number of Orthogonal Frequency Division Multiplexing (OFDM) symbols transmitting the PDCCH in a subframe, and is sent in a first OFDM symbol of the subframe, and the frequency location thereof is determined by a system downlink bandwidth and a cell identity (ID).
The PHICH is used for bearing the feedback information about positive acknowledgement/negative acknowledgement (ACK/NACK) of uplink transmission data. The number of the PHICH and the time-frequency location thereof can be determined by a system message and a cell ID in a Physical Broadcast Channel (PBCH) of a downlink carrier at which the PHICH locates.
The PDCCH is used for bearing Downlink Control Information (DCI), the DCI includes uplink and downlink scheduling information and uplink power control information. DCI formats are divided into the following types: DCI format 0, DCI format 1, DCI format 1A, DCI format 1B, DCI format 1C, DCI format 1D, DCI format 2, DCI format 2A, DCI format 3, DCI format 3A, etc., wherein:
the DCI format 0 is used for indicating the scheduling of a Physical Uplink Shared Channel (PUSCH);
the DCI format 1, the DCI format 1A, the DCI format 1B, the DCI format 1C and the DCI format 1D are used for PDSCH codeword scheduling in different modes;
and the DCI format 2, the DCI format 2A and the DCI format 2B are used for space division multiplexing in different modes;
and the DCI format 3 and the DCI format 3A are used for power control instructions of a Physical Uplink Control Channel (PUCCH) and the PUSCH in different modes.
The physical transmission resource of the physical downlink control channel (PDCCH) takes Control Channel Element (CCE) as unit, the size of one CCE is 9 Resource Element Groups (REG), i.e. 36 Resource Elements, and one PDCCH may occupy 1, 2, 4 or 8 CCE(s). As regards the sizes of these four-type PDCCHs occupied 1, 2, 4 and 8 CCE(s), an arborescence aggregation is used, that is to say, the PDCCH occupied by 1 CCE can start from any CCE location; the PDCCH occupied by 2 CCEs starts from an even number of CCE location; the PDCCH occupied by 4 CCEs starts from CCE location of an integer multiplied by 4; and the PDCCH occupied by 8 CCEs starts from CCE location of an integer multiplied by 8.
Each Aggregation level defines a search space, which includes a common search space and a User Equipment Specific (UE-Specific) search space. The number of CCEs of the whole search space is determined by the number of OFDM symbolic number and the number of the PHICH group which are occupied by a control domain instructed by the PCFICH in each downlink subframe. The UE performs blind detection on all the possible PDCCH code rates in the search space according to a DCI format in which the transmission mode is.
In the kth subframe, a control domain bearing the PDCCH consists of NCCE,k CCEs of which a group numbers are from 0 to NCCE,k−1. The UE should detect a group of PDCCH candidates in each non-DRX (non-Discontinuous Reception) subframe so as to acquire control information, and the detection means decoding the PDCCHs in the group according to all the DCI formats to be detected. The PDCCH candidates required to be detected are defined in a manner of search space, as regards aggregation level Lε{1, 2, 4, 8}, the search spaced is defined by a group of PDCCH candidates. In the search space Sj(L) the CCE corresponding to the PDCCH candidate m is defined by the following formula:L·{(Yk+m)mod└NCCE,k/L┘}+1
where i=0, . . . , L−1, m=0, . . . , M(L)−1, M(L) is the number of PDCCH candidates to be detected in the search space. Sk(L) As regards the common search space, where Yk=0, L takes 4 and 8. As regards the UE-specific search space, L takes 1, 2, 4 and 8.Yk=(AYk−1)mod D, 
where Y−1=nRNTI≠0, A=39827, D=65537, k=└ns/2┘, ns is a time slot number in a radio frame. nRNTI is a corresponding RNTI (Radio Network Temporary Identifier).
The UE should detect one common search space in each of which the aggregation levels are 4 and 8 respectively, and one UE-specific search space in each of which the aggregation levels are 1, 2, 4 and 8 respectively, and a common search space and a UE-specific search space can overlap. Particular the number of times of detection and a corresponding search space are shown in Table 1:
TABLE 1Number ofSearch space Sk(L)PDCCHTypeAggregation level LSize [in CCEs]candidates M(L)UE-specific16621264828162Common41648162
The UE is set as a transmission mode based on the followings through high-layer signalling semi-statically, receiving PDSCH data transmission according to the instruction of the PDCCH of the UE-Specific search space:
Mode 1: Single-antenna port; and port 0
Mode 2: Transmit diversity
Mode 3: Open-loop spatial multiplexing
Mode 4: Closed-loop spatial multiplexing
Mode 5: Multi-user multiple input multiple output (Multi-user MIMO)
Mode 6: Closed-loop Rank=1 precoding
Mode 7: Single-antenna port; and port 5
If the UE is set by a high-layer to use a Cyclical Redundancy Check (CRC) which is scrambled by a Cell Radio Network Temporary Identifier (C-RNTI) to decode the PDCCH, the UE should decode the PDCCH and all the relevant PDSCHs according to corresponding combination defined in table 2:
TABLE 2UEdownlinktransmissionPDCCH corresponding tomodeDCI formatSearch spacePDSCH transmission planMode 1DCI format 1ACommon search space, UEA single-antenna port, port 0specific search spacedefined by C-RNTIDCI format 1UE specific search spaceA single-antenna port, port 0defined by C-RNTIMode 2DCI format 1ACommon search space,Transmission diversityUE specific search spacedefined by C-RNTIDCI format 1UE specific search spaceTransmission diversitydefined by C-RNTIMode 3DCI format 1ACommon search space,Transmission diversityUE specific defined by C-RNTIDCI format 2AUE specific search spaceOpen-loop spatial multiplexing ordefined by C-RNTItransmission diversityMode 4DCI format 1ACommon search space,Transmission diversityUE specific search spacedefined by C-RNTIDCI format 2UE specific search spaceClosed-loop spatial multiplexingdefined by C-RNTIor transmission diversityMode 5DCI format 1ACommon search space,Transmission diversityUE specific search spacedefined by C-RNTIDCI format 1DUE specific search spaceMulti-user multiple input multipledefined by C-RNTIoutputMode 6DCI format 1ACommon search space,Transmission diversityUE specific search spacedefined by C-RNTIDCI format 1BUE specific search spaceClosed-loop Rank = 1 precodingdefined by C-RNTIMode 7DCI format 1ACommon search space,If the number of PBCH antennaUE specific search spaceports is 1, a single-antenna port,defined by C-RNTIport 0, is used; otherwise,transmission diversityDCI format 1UE specific search spacea single-antenna port; port 5defined by C-RNTIMode 8DCI format 1ACommon search space,If the number of PBCH antennaUE specific search spaceports is 1, a single-antenna port,defined by C-RNTIport 0, is used; otherwise,transmission diversityDCI format 2BUE specific search spaceDual-layer transmission, port 7defined by C-RNTIand port 8; ora single-antenna port, port 7 or 8Mode 9DCI format 1ACommon search space,If the number of PBCH antennaUE specific search spaceports is 1, a single-antenna port,defined by C-RNTIport 0, is used; otherwise,transmission diversityDCI format 2CUE specific search spaceup to 8-layer transmission, port 7-defined by C-RNTIport 14
Since an LTE-Advanced network is accessible for the LTE user, an operation frequency band thereof requires to cover the current LTE frequency band, the operation frequency has no spectral bandwidth of continuous 100 MHz which is able to be distributed at this frequency band, therefore, a direct technology required to be solved by the LTE-Advanced is using the carrier aggregation technology to aggregate several continuous component carrier frequencies (frequency spectrum) distributed at different frequency bands so as to form 100 MHz bandwidth which is able to be used by the LTE-Advanced. That is to say, as regards the aggregated frequency spectrum, it is divided into n component carrier frequencies (frequency spectrum), the frequency spectrum in each component carrier frequency (frequency spectrum) is continuous.
In the Release 11, a future release of the LTE-Advanced, since the requirements for user access increase, the original physical downlink control channel (PDCCH) resources will be insufficient to satisfy the requirements for a new release. Meanwhile, in a scenario of heterogeneous networks, since there is strong interference between different types of base stations, the problem of a macro eNodeB interfering with a micro eNodeB (Pico) and the problem of a home eNodeB interfering with a macro eNodeB require to be well solved.